1. Field of the Invention
The present invention generally relates to internet protocol (IP) telephones, and specifically relates to realizing various functions on IP telephones.
2. Description of the Related Art
In conventional internet protocol (IP) telephones, a transferring function, a caller ID function, and the like have been realized by using a session initiation protocol (SIP) server.
Japanese Patent Laid-Open Publication No. 2005-252809 discloses a technology that can transfer telephone calls without using the SIP server. However, according to the disclosed technology, calls can be transferred only from a telephone set that has a dedicated call-transferring function and the call can be transferred only to pre-registered telephone numbers. As a result, the conventional technology can only be used with IP telephone terminals in an internal-telephone line system, moreover, there is a need to set extension numbers and the like in advance.
Thus, there is a need of a technology that allows realization of various functions on IP telephones easily and with simpler configuration.